This document contains lecture notes on agricultural machinery design. It outlines the current state of agricultural machinery in the Philippines, which focuses on developing tillers, pumps, transplanters and other equipment. It then discusses the classifications, general considerations and procedures for machine design, including standards, economics, stresses, uncertainties and units. The notes provide an introduction to the topic and outline the key aspects that will be covered.

1. Lecture Notes
Agricultural Machinery Design
Engr. Elman C. Torres
Registered Philippine Agricultural Engineer
Chapter 1 - Introduction to Agricultural Machinery Design
Topic Outline
1. Current Status of Agricultural Machinery in the Philippines
2. Agricultural Machinery Design
3. Classifications of Machine Design
4. General Consideration in Machine Design
5. General Procedure in Machine Design
6. Standards and Codes
7. Economics
8. Stress and Strength
9. Uncertainty
10. Units
1 - Current Status of Agricultural Machinery in the Philippines
Agriculture is the primary industry of the Philippines Agricultural development
can be speed up through mechanization. Increase in crop production and reduction in
postharvest losses can be achieved by the use of appropriate agricultural machines. At
present, there is a limited supply of locally available designs of agricultural machines is
the Philippines.
Research and development efforts (on agricultural machinery) in the Philippines
is focusing on power tillers and hydrotillers, irrigation pumps, rice transplanters, drum
seeders, weeders, rice reapers, rice threshers, rice strippers, corn threshers and shellers,
village rice mills, grain moisture meters, coconut husk decorticators, abaca extractor, and
grain and copra dryers (Suministrado,2001)
The agricultural machinery industry in the Philippines has the following
characteristics:
1. Import of heavy machines and prime movers, and local assembly and fabrication
of small equipment; and

2. 2. Locally manufactured machines have high import content sometimes constituting
more than half of the total machinery cost.
2 - Agricultural Machinery Design
The subject Agricultural Machinery Design is the creation of new and better
agricultural machines and improving the existing ones. A new or better agricultural
machine is one which is more economical in the overall cost of production and operation.
The process of design is a long and time consuming one. From the study of existing
ideas, a new idea has to be conceived.
3 - Classifications of Machine Design
The machine design may be classified as follows:
1. Adaptive Design. The designer only makes minor alternation or modification in
the existing designs of the product.
2. Development Design. In this case, though the designer starts from the existing
design, but the final product may differ quite markedly from the original product.
3. New Design. This type of design needs lot of research, technical ability and
creative thinking. Only those designers who have personal qualities of a
sufficiently high order can take up the work of a new design.
The designs, depending upon the methods used, may be classified as follows:
1. Rational Design. This type of design depends upon mathematical formulae of
principle of mechanics.
2. Empirical Design. This type of design depends upon empirical formulae based
on the practice and past experience.
3. Industrial Design. This type of design depends upon the production aspects to
manufacture any machine component in the industry.
4. Optimum Design. It is the best design for the given objective function under the
specified constraints. It may be achieved by minimizing the undesirable effects.

3. 5. System Design. It is the design of any complex mechanical system like a motor
car.
6. Element Design. It is the design of any element of the mechanical system like
piston, crankshaft, connecting rod, etc.
7. Computer Aided Design. This type of design depends upon the use of computer
systems to assist in the creation, modification, analysis and optimization of a
design.
4 - General Consideration in Machine Design
Following are the general considerations in designing a machine component:
1. Type of load and stresses caused by the load.
2. Motion of the parts or kinematics of the machine
3. Selection of materials
4. Form and size of the parts
5. Frictional resistance and lubrication
6. Convenient and economical features
7. Use of standard parts
8. Safety of operations
9. Workshop facilities
10. Number of machines to be manufactured
11. Cost of construction
12. Assembling
5 - General Procedure in Machine Design
In designing a machine component, there is no rigid rule. The problem may be
attempted in several ways. However, the general procedure to solve a design problem is
as follows:
1. Recognition of need
2. Synthesis (Mechanisms)
3. Analysis of forces
4. Material Selection
5. Design of elements (Size and Stresses)
6. Modification
7. Detailed drawing

4. 8. Production
6 – Standards and Codes
A standard is a set of specifications for parts, materials, or processes intended to
achieve uniformity, efficiency, and a specified quality. One of the important purposes of
a standard is to limit the multitude of variations that can arise from the arbitrary creation
of a part, material, or process.
A code is a set of specifications for the analysis, design, manufacture, and
construction of something. The purpose of a code is to achieve a specified degree of
safety, efficiency, and performance or quality. It is important to observe that safety codes
do not imply absolute safety.
Listed below have established specifications for standards and safety or design
codes in the Philippines.
1. Philippine Agricultural Engineering Standards
2. Philippine National Standards
7 – Economics
The consideration of cost plays such an important role in the design decision
process that we could easily spend as much time in studying the cost factor as in the
study of the entire subject of design.
1. Standard Sizes. The use of standard or stock sizes is a first principle of cost
reduction.
2. Large Tolerances. Among the effects of design specifications on costs,
tolerances are perhaps most significant. Tolerances, manufacturing processes, and
surface finish are interrelated and influence the producibility of the end product in
many ways.
3. Cost Estimates. Many other cost estimators can be used, depending upon the
application, such as area, volume, horsepower, torque, capacity, speed, and
various performance ratios.
4. Breakeven Points. Sometimes it happens that, when two or more design
approaches are compared for cost, the choice between the two depends on a set of

5. conditions such as the quantity of production, the speed of the assembly lines, or
some other condition. There then occurs a point corresponding to equal cost,
which is called the breakeven point.
8 – Stress and Strength
1. Strength
a. An inherent property of a material or of a mechanical element
b. Depends on treatment and processing
c. May or may not be uniform throughout the part
d. Examples: Ultimate strength, yield strength
2. Stress
a. A state property at a specific point within a body
b. Primarily a function of load and geometry
c. Sometimes also a function of temperature and processing
9 - Uncertainty
Uncertainties in machinery design abound. Examples of uncertainties concerning
stress and strength include
1. Composition of material and the effect of variation on properties.
2. Variations in properties from place to place within a bar of stock.
3. Effect of processing locally, or nearby, on properties.
4. Effect of nearby assemblies such as weldments and shrink fits on stress
conditions.
5. Effect of thermomechanical treatment on properties.
6. Intensity and distribution of loading.
7. Validity of mathematical models used to represent reality.
8. Intensity of stress concentrations.
9. Influence of time on strength and geometry.
10. Effect of corrosion.
11. Effect of wear.
12. Uncertainty as to the length of any list of uncertainties.
10 – Units
The measurement of physical quantities is one of the most important operations in
engineering. Every quantity is measured in terms of some arbitrary, but internationally
accepted units, called fundamental units.

6. Table 1 – SI Base and Supplementary Units and their Symbols
Quantity Unit Symbol of SI Unit
Base Units:
1. length meter m
2. mass kilogram kg
3. time second s
4. electric current ampere A
5. thermodynamic temperature kelvin K
6. amount of substance mole mol
7. luminous intensity candela cd
Supplementary units:
1. plane angle radian rad
2. solid angle steradian sr
References
BUDYNAS, R.G. and NISBETT, J.K. 2011. Shigley’s Mechanical Engineering Design,
Ninth Edition. McGraw-Hill Companies Inc.. New York.
KHURMI, R.S. and GHUPTA, J.K. 2005. Machine Design (S.I. Units). Eurasia
Publishing House (PVT.) LTD. Ram Nagar, New Delhi.
PAES 020:2005 – General – Metrication Guidelines
SUMINISTRADO, D.C. 2001. Status of Agricultural Mechanization in the Philippines.